The formula to the solution is as follows: x = amount spent per person d = drink p = popcorn and vc = veggie cup this makes (p+vc)/2 = they shared the poppcorn and the veggie cup and thus the sum musst be divided by the amount of sharing people which is two. => x = d + (p+vc)/2 And since there is no money mentioned for the movies (m) it is teh formula above. If you would like to consider that costs too it would be: x = m + d + (p+vc)/2